Clinical and Hematological Follow-Up of Long-Term Oral Therapy with Type-I Interferon in Cats Naturally Infected with Feline Leukemia Virus or Feline Immunodeficiency Virus.

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV), two of the most important pathogens of cats, produce chronic systemic diseases with progressive death of cells involved in the immune response, ultimately leading to death. Immunostimulants is one of the few alternatives to the symptomatic treatment. In this study, 27 naturally FeLV-infected (FeLV+) and 31 naturally FIV-infected (FIV+) cats were administered orally by their owners 60 IU/day of recombinant human interferon alpha (rHuIFN-α) for four months in alternate weeks. Clinical status was evaluated and blood samples collected at four different visits or months (M): pretreatment (M0), mid-treatment (M2), end of treatment (M4), and 4-8 months after end of treatment (M10). Most cats ostensibly improved their clinical status, and many became asymptomatic. rHuIFN-α treatment improved the anemic processes observed at M0 (at least in cats with mild or moderate anemia) and leukocyte counts, including a more favorable CD4+/CD8+ ratio. An increase in the serum gammaglobulin concentration was seen in 80% of the cats. Despite observing an obvious favorable progress in the clinical, biopathological, and CD4+/CD8+ values during treatment, almost invariably all the parameters analyzed worsened after treatment discontinuation (M10), which suggests that the interferon-α protocol should be either extended or include additional cycles for a long-lasting benefit in FeLV+ and FIV+ cats.

Follow-Up of Viral Parameters in FeLV- or FIV-Naturally Infected Cats Treated Orally with Low Doses of Human Interferon Alpha.

Specific treatments for the long-life infections by feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are either toxic, expensive or not too effective. Interferon α (IFN-α) is an immunomodulatory molecule which has been shown in vitro to decrease the release of infective particles. The aim of this study was to follow the progress of the clinical score and viral parameters of FeLV- and FIV-naturally infected privately owned cats treated with recombinant human IFN-α (rHuIFN-α, Roferon-A). Twenty-seven FeLV-infected cats (FeLV+) and 31 FIV-infected cats (FIV+) were enrolled in the study. Owners were instructed to orally administer 1 mL/day of 60 IU rHuIFN-α/mL in alternating weeks for four months. Blood samples were taken at the beginning of the study (M0), mid-treatment (M2), end of treatment (M4), and 6-10 months later (M10). Clinical status at these time points improved notably with rHuIFN-α treatment, regardless of the initial severity of the disease, an effect which lasted throughout the study in most animals (15 of the 16 FeLV+ symptomatic cats; 20 of the 22 FIV+ symptomatic cats) improved markedly their clinical situation. In FeLV+ cats plasma antigenemia (p27CA), reverse transcriptase (RT) activity, and proviral load decreased at M2 and M4 but increased again at M10 ("rebound effect"). The level of antigenemia or RT activity was below the detection limits in FIV+ cats, and the effect on proviral load was less marked than in FeLV+ cats. Taken together, these results indicate that rHuIFN-α is a good candidate for treating FeLV+ cats, but the "rebound effect" seen when treatment was discontinued suggests that additional studies should be conducted to clarify its effect on progression of the infection in cats.

Use of recombinant interferon omega in feline retrovirosis: from theory to practice.

Type-I interferons (IFNs) are cytokines that have non-specific antiviral activity, participating mostly in innate defense mechanisms. Their administration has been proposed to treat several viral and immunomediated diseases as an immunomodulatory therapy. Due to its availability, recombinant human interferon-alpha (rHuIFN-α) has been studied in relation to feline retrovirosis, both in vitro and in vivo. However, IFNs are species-specific and antibodies have been shown to develop in response to the high rHuIFN-α doses necessary for an effective therapy. A recombinant feline IFN has been developed, which has been characterized as interferon-omega (rFeIFN-ω), designed to overcome these problems. Nonetheless, very few studies have been undertaken to evaluate its efficacy in cats naturally infected with FIV or FeLV. In an initial study, we here demonstrated that rFeIFN-ω can dramatically improve the clinical condition of infected cats, and induce improvement of hematologic parameters. Minor changes or no change was observed for hypergammaglobulinemia, CD4/CD8 ratio, proviral load, viremia and RT activity, suggesting that the overall effect of IFN was on innate immunity. More studies are needed in order to better understand its in vivo mechanisms.

Strain differences in the dose-response relationship for morphine self-administration and impulsive choice between Lewis and Fischer 344 rats.

Dose-response studies are thought to be a valuable tool to predict the most genetically drug-vulnerable individuals. However, dose-response curves for morphine self-administration have not yet been examined and nor strain differences might be evident. Therefore, this study aimed to define the dose-response curve for morphine self-administration (0.25, 0.5, 1 and 2 mg/kg) in Lewis (LEW) rats and their histocompatible Fischer-344 (F344) rats. In addition, impulsivity has been suggested as one of the genetic factors contributing most to the initiation of drug use. Therefore, the impulsive choice of both rat strains in the presence or absence of the same morphine doses was also analysed. LEW rats self-administered significantly more morphine whatever the dose tested and they exhibited greater basal impulsive choice compared with F344 rats. The F344 strain showed a preference for the dose of 0.5 mg/kg, while any of the doses used had a differential reinforcing effect in the LEW strain. The basal pattern of strain differences in impulsive choice was not affected by morphine administration. These data suggest that the LEW strain has a highly drug-vulnerable phenotype and they point to the strength of impulsivity as a pre-existing behavioural trait that might make this rat strain more vulnerable to the reinforcing effects of drugs and, therefore, to develop addiction.

Strain differences between Lewis and Fischer 344 rats in the modulation of dopaminergic receptors after morphine self-administration and during extinction.

The Lewis (LEW) and Fischer 344 (F344) rat strains have been used as a model to study genetic vulnerability to drug addiction and they differ in their dopaminergic systems. We have studied the variation in the D1-like and D2-like receptors in distinct brain regions of LEW and F344 rats that self-administered morphine (1 mg/kg) for 15 days and also after different extinction periods (3, 7 and 15 days). Under basal conditions, binding to D1-like receptors in the olfactory tubercle and substantia nigra, and to D2-like receptors in the Pyriform cortex and hippocampal-CA1 was lower in LEW rats than in F344 rats. Conversely, the LEW rats exhibited stronger D2-like binding in the caudate-putamen. In most brain regions there was a decrease in D1-like binding in LEW rats after self-administration while the F344 animals displayed an increment. Additionally, D2 receptors of LEW rats were down-regulated after self-administration in the caudate-putamen and in the nucleus accumbens (shell and core divisions). Binding to D1-like receptors increased in both strains in the early phases of extinction, while in the later stages a differential regulation was observed between both strains. During the early phases of extinction only F344 rats showed alterations in D2-like receptor binding, however in the latter phases a specific modulation occurred in both strains. These differences in basal D1-like and D2-like receptor binding, and their differential modulation after self-administration and during extinction, may be reflected in the greater vulnerability to opiate addiction shown by LEW strain.

Effect of type I interferons on the expression of feline leukaemia virus.

The efficacy of interferons (IFNs), used empirically to treat retrovirus-infected cats has been shown in vivo, but the direct effect on infected cells is largely unknown. Ten-fold serial dilutions of three recombinant IFNs available for therapy, human IFNalpha(2a), IFNalpha(A/D) and feline IFNomega were added to the chronically FeLV-infected cell line FL74. IFNs did not apparently affect viral protein expression. However, reverse transcriptase activity (RT), directly proportional to the amount of infectious free virions, decreased with increasing concentrations of IFN and longer treatment times. The induction of apoptosis by IFN was suspected. Results of its evaluation by annexin V-Fluos staining showed that IFNs decreased the viability of treated FeLV-infected cells, and increased apoptosis, but not of non-infected cells. According to the IC(50), rHuIFNalpha(A/D) appeared to be the most effective IFN in inhibiting RT.

Modulation of the endogenous opioid system after morphine self-administration and during its extinction: a study in Lewis and Fischer 344 rats.

Lewis (LEW) and Fischer 344 (F344) rats show differential morphine self-administration rates. In this study, after animals of both strains self-administered morphine (1mg/kg) or extinguished this behaviour for 3, 7 or 15days, we measured the binding to, and functional state of mu opioid receptors (MORs) as well as proenkephalin (PENK) mRNA content in several brain regions. The results showed that in most brain areas: 1) LEW rats had less binding to MORs in basal conditions than F344 rats; 2) after morphine self-administration, either one of the strains or both (depending on the brain area) showed increased levels of binding to MORs as compared to basal groups; and 3) these binding levels in morphine self-administration animals came down in each extinction group. Moreover, F344 rats exhibited, in general, an increased functionality of MORs after morphine self-administration, as compared to basal groups, which also went down during extinction. Finally, the basal content of PENK mRNA was lower in LEW rats than in F344 rats and it decreased more after self-administration; during extinction, the levels of PENK mRNA got normalized in this strain. This differential modulation of the endogenous opioid system might be related to the different rates of morphine self-administration behavior exhibited by both inbred rat strains.

Repeated administration with Delta9-tetrahydrocannabinol regulates mu-opioid receptor density in the rat brain.

Several studies have demonstrated reciprocal, as well as synergistic interactions between cannabinoid and opioid systems. The aim of this study was to explore the time-related effects of repeated administration of Delta9-tetrahydrocannabinol on mu-opioid receptor autoradiography in various brain regions of the rat. To this aim, the effects of Delta9-tetrahydrocannabinol (Delta9-THC, 5 mg/kg/day; i.p.) were examined after 1, 3, 7 and 14 days of repeated administration on regions containing mu-opioid receptors: (i) forebrain [caudate-putamen, nucleus accumbens (core and shell) and piriform cortex]; (ii) amygdala (medial pars and cortical posteromedial pars), hypothalamus (ventromedial and dorsomedial nuclei, zona incerta), hippocampal regions (CA1, CA2, CA3, dentate girus), hindbrain (substantia nigra and ventral tegmental area); and (iii) thalamus, including 12 thalamic nuclei. In most of these regions, repeated cannabinoid administration increases mu-opioid receptor density; however, the onset, degree of magnitude reached and time-related effects produced by administration with Delta9-tetrahydrocannabinol are dependent upon the brain region examined. It appears that the major increase in mu-opioid receptor density occurs 1 and 3 days after Delta9-THC administration. In some regions, this increase is maintained and, for most of the brain areas examined, this effect is no longer significant by 14 days of administration, suggesting tolerance to cannabinoid treatment. Taken together, the results of this study suggest that cannabinoids produce a time-related differential responsiveness in mu-opioid receptor density in several brain areas that may be relevant to an understanding of the alterations associated with cannabinoid exposure.

Effects of perinatal exposure to delta 9-tetrahydrocannabinol on operant morphine-reinforced behavior.

The present study examined the effects of Delta(9)-tetrahydrocannabinol (Delta(9)-THC) when administered during the perinatal period on morphine self-administration in adulthood. To this end, pregnant Wistar rats were daily exposed to Delta(9)-THC from the fifth day of gestation up to pup weaning, when they were separated by gender and left to mature to be used for analyses of operant food- and morphine-reinforced behavior in a progressive ratio (PR) schedule. We also analyzed dopaminergic activity (DOPAC/DA) in reward-related structures during specific phases of the behavioral study. In both reinforcement paradigms, food and morphine, females always reached higher patterns of self-administration than males, but this occurred for the two treatment groups, Delta(9)-THC or vehicle. These higher patterns measured in females corresponded with a higher DOPAC/DA in the nucleus accumbens prior to the onset of morphine self-administration in comparison to males. Interestingly, DOPAC/DA was lower in Delta(9)-THC-exposed females compared to oil-exposed females and similar to oil- and Delta(9)-THC-exposed males. In addition, Delta(9)-THC-exposed females also exhibited a reduction in DOPAC/DA in the ventral tegmental area, which did not exist in males. All these changes, however, disappeared after 15 days of morphine self-administration and they did not reappear after 15 additional days of extinction of this response. Our data suggest that females are more vulnerable than males in a PR schedule for operant food and morphine self-administration; perinatal Delta(9)-THC exposure is not a factor influencing this vulnerability. The neurochemical analysis revealed that the activity of limbic dopaminergic neurons prior to morphine self-administration was higher in females than males, as well as that the perinatal Delta(9)-THC treatment reduced the activity of these neurons only in females, although this had no influence on morphine vulnerability in these animals.

Genetic differences in NMDA and D1 receptor levels, and operant responding for food and morphine in Lewis and Fischer 344 rats.

Previously, we have shown that Lewis (LEW) rats acquire faster than Fischer 344 (F344) rats operant food- and morphine-reinforced tasks under fixed-ratio schedules of reinforcement. The first purpose of the present work has been to study if differences in operant responding behavior may participate in the reported differences in morphine self-administration behavior between both inbred rat strains. To this end, we have analyzed the microstructure of responding obtained under a variable-interval (VI) of food reinforcement by calculating the inter-response time (IRT) for each rat strain. LEW rats exhibited shorter IRTs than F344 rats, suggesting that LEW rats may have an inherent high or compulsive operant responding activity. When subjects of both inbred rat strains were submitted to a schedule of morphine reinforcement of high responding requirements such as progressive ratio schedules, LEW rats also reached significantly higher breaking points and final response ratio than F344 rats for i.v. morphine self-administration. Given that there are neurochemical differences between both rat strains and that glutamatergic N-methyl-D-aspartate (NMDA) and dopaminergic D(1) receptors have been involved in operant responding behavior, a second purpose of this work has been to measure basal NMDA and D(1) receptor levels in these rat strains by quantitative receptor autoradiography. Compared to F344 rats, LEW rats showed higher basal NMDA receptor levels in frontal and cingulate cortex, caudate putamen, central amygdaloid nuclei, and intermediate white layer of superior colliculus, and higher basal D(1) receptor levels in several areas of hippocampus and thalamus, and substantia nigra pars reticulata. Taken together, these results suggest that an inherent high operant responding activity of LEW rats may have a role in the previous reported faster acquisition of opiate-reinforced behavior in operant self-administration paradigms under fixed-ratio schedules of reinforcement. In addition, a basal higher NMDA and D(1) receptor levels of LEW rats compared to F344 rats may participate in the neurochemical background that mediates the behavioral differences between both inbred rat strains.

Neuroadaptaciones en los sistemas Glutamatérgico y Dopaminérgico durante la abstinencia de cocaína / Neuroadaptative changes in dopaminergic and glutamatergic receptor subtypesafter extinction of cocaine self-administration behavior

El fenómeno de las recaídas en la adicción a drogas tras un periodo de abstinencia mantenido sigue siendo uno de los retos más difíciles de resolver. La vuelta al consumo produce, entre otros efectos, un gran desconcierto en el ex-abstinente y desorientación y desmotivación en los profesionales y el entorno familiar. Los factores que pueden facilitar un proceso de recaída son múltiples pero, en general, se incluyen en dos grandes grupos: los exógenos (fácil acceso a la sustancia; pertenencia a determinados grupos sociales...etc) y los endógenos (disfunciones de sistemas de neurotransmisores; condicionamiento a estímulos externos, la personalidad del sujeto; el estado mental...etc). Siendo obvia la importancia de los factores exógenos, hay cada día mayor cantidad de trabajos en la literatura científica que resaltan la posible función de los factores endógenos. En este trabajo presentaremos datos que demuestran la existencia de neuroadapataciones en los sistemas glutamatérgico y dopaminérgico tras la extinción de la conducta de autoadministración de cocaína en diversas regiones cerebrales de roedores de laboratorio. Esas neuroadaptaciones son más permanentes y duraderas en el sistema dopaminérgico. Considerados globalmente, estos resultados sugieren que durante la abstinencia de psicoestimulantes pueden producirse neuroadaptaciones en distintos sistemas de neurotransmisores que pueden mantener el deseo por la droga, exacerbar la potencialidad de los estímulos condicionados, incrementar la ansiedad...etc, y favorecer, en definitiva, una mayor vulnerabilidad a la recaída (AU)